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Lionfish Definition
A lionfish is nocturnal carnivorous fish belonging to the genus Pterois that can grow up to 15 inches in length. These solitary fishes have a life span of 5-15 years and are venomous.
What is Lionfish?
The lionfish belongs to the genus that comprises 12 species that are native to tropical marine waters of the Indo-pacific region. They can be found at great depth in mangroves, hard bottom, coral, artificial reefs, and corals. They are considered invasive species in the Gulf of Mexico and Western Atlantic Ocean where they were introduced.
They belong to the Scorpaenidae family that have characteristic venomous sharp spines. The Pterois genus fishes all have long pectoral fins, that resemble the mane of a lion. Lionfishes have needle-like fins that are venomous and are 18 in number and soft-fins in addition to that.
These venomous fins cover the undersides and backs of the fishes and are involved in defense against predators. They exhibit aposematic warning coloration showing white, red, brown, cream, or black stripes to warn the predators of its venomous nature.
They reproduce throughout the year, with the females producing 2 million eggs per year. Lionfish reproduce year-round and a single mature female release around 2 million eggs per year. The average clutch size is around 30,000 eggs.
The different species of the genus show similar courtship behaviors, they either follow the female fishes or circle around them. After courtship the female releases 2 masses of eggs that are then fertilized by the males.
Fertilized buoyant egg masses are bound together by adhesive mucus. The individual embryos break free from the disintegrating mucus and become free-floating.
Lionfish Hunting and Predation
Lionfish use anal fins and dorsal fins to move slowly in the forward direction. Even though they propel and advance slowly they can regulate their buoyancy with the aid of bilateral swim bladder muscles that make them good hunters. They can adjust their position on the water table by altering their center of gravity in the angle best to attack the prey.
They attack their prey near reefs or rocks, corner their prey against the rocks, spread their large pectoral fins to attack them, and then swallow them whole. They prey on invertebrates like shrimp, mollusks, and small fish.
They are not limited to any specific fishes for their food but prey on a rather wide variety of fish species. Their stomachs can expand up to 30 times their original size to accommodate the enormous amount of meals as they have a large appetite. They feed actively from 7 to 11 am, though they are grouped as nocturnal.
During the rest of the time, they may rest among reefs or crevices amongst rocks. They have a number of natural predators like Bobbit worms, moray eels, nurse sharks, large groupers, and blue-spotted cornetfish, despite lionfish being venomous fish.
These predators may found a mechanism to tolerate and built resistance to the lionfish venom. These species also depict cannibalism besides inter-specific predation. The larger adult fishes prey on the smaller members of their species.
Fun Facts About Lionfish
In the course of evolution, they have evolved to be very skilled predators and dangerous prey. These characteristics also make them invasive if introduced in a new habitat.
i. Lionfish is a Invasive Species
Two species of lionfish have become invasive in the regions they were introduced to. These are the common lionfish and the red lionfish that are now present in non-native places like the Gulf of Mexico and the Western Atlantic ocean. The red lionfish constitutes up to 93% of the invasive population of the Western Atlantic Ocean.
These invasive species on introduction alter the ecological processes of the non-native region and can cause environmental, ecological, and economic damage. Some examples of other invasive species include gray squirrels, kudzu vine, and carp.
They were first introduced as a form of pets and they later spread to the eastern coast of Florida. These invasive species generally lack a natural predator in the introduced regions that allows an exponential increase in their population in absence of predators that can keep their population under check. This happened with lionfish also, they had no predators in these introduced regions of the east coast of America.
They have a vicious appetite that will cause a significant decrease in their prey population that includes native fishes. In the Bahamas, they caused a 65-95% decline in the population of native fishes. Local authorities have encouraged people to capture such invasive species to decrease their population.
ii. Lionfish is a Venomous Fish
In the spines of lionfish, 2 glandular grooves are present that extends from the base to reach the top of the spine. These glands release venom when mechanical disruption of fins occurs. This venom comprises the neurotransmitter acetylcholine, some proteins, and a neurotoxin that causes pain, paralysis, and respiratory failure.
The sting of a lionfish is extremely painful as they target nerve cells that relay pain signals. This venom has evolved them to defend themselves against predators as they are slow-moving fishes and may face trouble escaping from predators.
iii. Lionfish and Camouflage
The contrasting bold stripes comprise an aposematic warning to predators. But they serve another purpose that is to aid in camouflaging so that lionfish can easily sneak and attack their prey.
There are also several fleshy extensions on their head that resemble algal growths and help disguise their mouths. They can also hide well using this camouflage of brown and red colouration and remain motionless to hide from their prey or predators.
Lionfish Citations
- Lionfish envenomation in Caribbean and Atlantic waters: Climate change and invasive species. Int J Womens Dermatol . 2020 Jul 4;7(1):120-123.
- The lionfish Pterois sp. invasion: Has the worst-case scenario come to pass? J Fish Biol . 2018 Mar;92(3):660-689.
- Aquatic antagonists: lionfish (Pterois volitans). Cutis . 2006 Apr;77(4):215-6.
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